METHOD FOR MONITORING A COMMUNICATION CONNECTION BETWEEN TWO NETWORK NODES THAT ARE DIRECTLY CONNECTED TO ONE ANOTHER

1 . A method for ascertaining a limit value for the signal transit time on a connection between two network nodes, directly connected to one another, of a system comprising a large number of network nodes that are connected via a network, wherein the method comprises:

a) ascertaining the signal transit time between the network nodes that are directly connected to one another,

wherein the method is characterized by the steps:

b) initiating a message of a first type via the direct connection, to which message there is added or assigned in the transmitter a transmission timestamp and/or in the receiver a reception timestamp,

c) delaying the message, after the transmission timestamp has been set and before the message is transmitted via the physical layer and/or after the message has been received via the physical layer and before the reception timestamp is set, by a first value or in each case by first values,

d) transmitting the message with a delay via the physical layer,

e) checking whether the signal transit time has exceeded a predetermined value,

f1) repeating steps c) to e) with a delay value or delay values which has/have been increased in each case relative to the previously set delay value or relative to the previously set delay values, until the signal transit time has exceeded the predetermined value, and

h) storing and/or outputting the last delay value or the last delay values as the ascertained limit value or the ascertained limit values for the direct connection at which the signal transit time has not yet exceeded the predetermined value.

2 . The method as claimed in claim 1 , additionally comprising, after the signal transit time has exceeded the predetermined value for the first time in step f1):

f2) repeating steps c) to e) with the previously set delay value or the previously set delay values until the signal transit time has exceeded the predetermined value in a previously defined number of tests or repetitions in succession, wherein, if the signal transit time has fallen below the predetermined value again before the defined number of tests or repetitions has been reached, the method is repeated with step c) and a delay time that is increased again.

3 . The method as claimed in claim 1 , additionally comprising, after the signal transit time has exceeded the predetermined value in step f1) or has exceeded a previously defined number of tests or repetitions in succession in step f2):

g2) repeating steps c) to e) with a delay value or delay values which has/have been reduced in each case relative to the previously set delay value or relative to the previously set delay values, until the signal transit time no longer exceeds the predetermined value.

4 . The method as claimed in claim 3 , additionally comprising, after the signal transit time has fallen below the predetermined value for the first time in step g2):

g3) repeating steps c) to e) with the previously set delay value or the previously set delay values until the signal transit time has fallen below the predetermined value in a previously defined number of tests or repetitions in succession, wherein, if the signal transit time has exceeded the predetermined value again before the defined number of tests or repetitions has been reached, the method is repeated with step c) and a delay time that is reduced again.

5 . The method as claimed in claim 3 , additionally comprising:

g1) initiating and transmitting without a delay a message of a first type via the direct connection, to which message there is added or assigned a transmission timestamp in the transmitter and/or a reception timestamp in the receiver, after each message transmitted with a delay, the signal transit time of which has exceeded the predetermined value.

6 . The method as claimed in claim 1 , wherein the delayed transmission comprises:

encrypting a message transmitted immediately before a message of the first type, and/or

encrypting at least the first type of messages after the transmission timestamp has been set,

and/or wherein the delayed receiving comprises:

decrypting the message received immediately before a message of the first type, and/or

decrypting at least the first type of messages before the reception timestamp is set.

7 . The method as claimed in claim 6 , wherein the setting of different delays comprises:

encrypting at least the first type of messages with different encryption parameters.

8 . A method for identifying an intervention in a direct connection between two network nodes of a system during operation, comprising:

repeatedly initiating, cyclically or at irregular intervals, messages of the first type, to which there is added or assigned a transmission timestamp in the transmitter and/or a reception timestamp in the receiver,

delaying at least the first type of messages, after the transmission timestamp has been set and before the message is transmitted via the physical layer and/or after the message has been received via the physical layer and before the reception timestamp is set, by an ascertained limit value or by ascertained limit values for the direct connection, wherein the ascertained limit value or the ascertained limit values are ascertained by:

b) initiating a message of a first type via the direct connection, to which message there is added or assigned in the transmitter a transmission timestamp and/or in the receiver a reception timestamp,

c) delaying the message, after the transmission timestamp has been set and before the message is transmitted via the physical layer and/or after the message has been received via the physical layer and before the reception timestamp is set, by a first value or in each case by first values,

d) transmitting the message with a delay via the physical layer,

e) checking whether the signal transit time has exceeded a predetermined value,

f1) repeating steps c) to e) with a delay value or delay values which has/have been increased in each case relative to the previously set delay value or relative to the previously set delay values, until the signal transit time has exceeded the predetermined value, and

h) storing and/or outputting the last delay value or the last delay values as the ascertained limit value or the ascertained limit values for the direct connection at which the signal transit time has not yet exceeded the predetermined value,

checking whether the signal transit time has exceeded a predetermined value,

wherein, if the signal transit time has exceeded a predetermined value, the method additionally comprises:

signaling that the limit value has been exceeded.

9 . The method as claimed in claim 8 , wherein, in response to the signaling, the system, or at least one of the network nodes, is transferred into an error operating mode or the delaying, at least for the first type of messages, is reduced to a value at which the signal transit time does not exceed a predetermined value.

10 . The method as claimed in claim 9 , wherein the delaying to a value at which the signal transit time does not exceed a predetermined value comprises ascertaining the limit value again by;

a) ascertaining the signal transit time between the network nodes that are directly connected to one another, further comprising:

b) initiating a message of a first type via the direct connection, to which message there is added or assigned in the transmitter a transmission timestamp and/or in the receiver a reception timestamp,

c) delaying the message, after the transmission timestamp has been set and before the message is transmitted via the physical layer and/or after the message has been received via the physical layer and before the reception timestamp is set, by a first value or in each case by first values,

d) transmitting the message with a delay via the physical layer,

e) checking whether the signal transit time has exceeded a predetermined value,

f1) repeating steps c) to e) with a delay value or delay values which has/have been increased in each case relative to the previously set delay value or relative to the previously set delay values, until the signal transit time has exceeded the predetermined value, and

h) storing and/or outputting the last delay value or the last delay values as the ascertained limit value or the ascertained limit values for the direct connection at which the signal transit time has not yet exceeded the predetermined value.

11 . A network node configured to communicate with another network node via a direct connection, having at least one processor, volatile and nonvolatile memory, and a network interface, wherein there are retrievably stored in the nonvolatile memory computer-executable instructions which, when they are executed by the at least one processor, configure the network node to ascertain a limit value for the signal transit time and/or for monitoring the integrity of the communication by performing operations comprising:

a) ascertaining the signal transit time between the network nodes that are directly connected to one another,

wherein the method is characterized by the steps:

b) initiating a message of a first type via the direct connection, to which message there is added or assigned in the transmitter a transmission timestamp and/or in the receiver a reception timestamp,

c) delaying the message, after the transmission timestamp has been set and before the message is transmitted via the physical layer and/or after the message has been received via the physical layer and before the reception timestamp is set, by a first value or in each case by first values,

d) transmitting the message with a delay via the physical layer,

e) checking whether the signal transit time has exceeded a predetermined value,

f1) repeating steps c) to e) with a delay value or delay values which has/have been increased in each case relative to the previously set delay value or relative to the previously set delay values, until the signal transit time has exceeded the predetermined value, and

h) storing and/or outputting the last delay value or the last delay values as the ascertained limit value or the ascertained limit values for the direct connection at which the signal transit time has not yet exceeded the predetermined value.

12 . A system, in particular a vehicle system, having two or more network nodes connected to one another in each case via direct connections, wherein at least one of the network nodes is a network node configured to communicate with another network node via a direct connection, having at least one processor, volatile and nonvolatile memory, and a network interface, wherein there are retrievably stored in the nonvolatile memory computer-executable instructions which, when they are executed by the at least one processor, configure the network node to ascertain a limit value for the signal transit time and/or for monitoring the integrity of the communication by performing operations comprising:

a) ascertaining the signal transit time between the network nodes that are directly connected to one another,

wherein the method is characterized by the steps:

b) initiating a message of a first type via the direct connection, to which message there is added or assigned in the transmitter a transmission timestamp and/or in the receiver a reception timestamp,

c) delaying the message, after the transmission timestamp has been set and before the message is transmitted via the physical layer and/or after the message has been received via the physical layer and before the reception timestamp is set, by a first value or in each case by first values,

d) transmitting the message with a delay via the physical layer,

e) checking whether the signal transit time has exceeded a predetermined value,

f1) repeating steps c) to e) with a delay value or delay values which has/have been increased in each case relative to the previously set delay value or relative to the previously set delay values, until the signal transit time has exceeded the predetermined value, and

h) storing and/or outputting the last delay value or the last delay values as the ascertained limit value or the ascertained limit values for the direct connection at which the signal transit time has not yet exceeded the predetermined value.

13 . (canceled)

14 . A non-transitory computer-readable medium having stored thereon computer-executable instructions that, when executed by a processor, cause performance of operations for ascertaining a limit value for the signal transit time on a connection between two network nodes, directly connected to one another, of a system comprising a large number of network nodes that are connected via a network, wherein the operations comprise:

a) ascertaining the signal transit time between the network nodes that are directly connected to one another,

wherein the method is characterized by the steps:

b) initiating a message of a first type via the direct connection, to which message there is added or assigned in the transmitter a transmission timestamp and/or in the receiver a reception timestamp,

c) delaying the message, after the transmission timestamp has been set and before the message is transmitted via the physical layer and/or after the message has been received via the physical layer and before the reception timestamp is set, by a first value or in each case by first values,

d) transmitting the message with a delay via the physical layer,

e) checking whether the signal transit time has exceeded a predetermined value,

f1) repeating steps c) to e) with a delay value or delay values which has/have been increased in each case relative to the previously set delay value or relative to the previously set delay values, until the signal transit time has exceeded the predetermined value, and

h) storing and/or outputting the last delay value or the last delay values as the ascertained limit value or the ascertained limit values for the direct connection at which the signal transit time has not yet exceeded the predetermined value.